(a) Field of the Invention
The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display having a wide viewing angle and a fast response speed, and in which liquid crystal molecules of the liquid crystal display have a uniformly bent alignment.
(b) Description of the Related Art
The liquid crystal display (LCD) is structured having liquid crystal material injected between two substrates. A voltage of a different potential is applied to electrodes of the substrates to form an electric field such that the alignment of liquid crystal molecules of the liquid crystal material is varied. Accordingly, the transmittance of incident light is controlled to enable the display of images.
Various LCD configurations have been developed to increase the response speed and viewing angle of such LCDs. Examples include the HAN (hybrid aligned nematic) LCD and the OCB (optically compensated bend) LCD. The OCB liquid crystal display includes an electrode on each substrate, the electrodes forming an electric field between the substrates where the substrates are perpendicular to the electric field; a liquid crystal layer formed by injecting liquid crystal material between the substrates; and an orientation layer formed on each substrate, the orientation layer aligning liquid crystal molecules of the liquid crystal layer in the same direction, substantially parallel to the substrates.
In such an OCB LCD, the liquid crystal molecules are aligned symmetrically about an imaginary center plane that is parallel and equidistant to the two substrates. In particular, the liquid crystal molecules are substantially parallel to the substrates at areas adjacent to the substrates, then they increasingly bend to a vertical position in a direction toward the imaginary center plane, at which point the liquid crystal molecules are substantially perpendicular to the substrates. Such an alignment is obtained through the combination of the orientation layers, which align the liquid crystal molecules parallel to the substrates, and the generated electric field, which provides a force to align the liquid crystal molecules perpendicular to the substrates. Because the liquid crystal molecules move in the same direction when driving the OCB LCD, a wide viewing angle and a fast response speed are achieved.
However, a serious drawback of the OCB LCD is that a broken or non-uniform alignment of the liquid crystal molecules results at areas where orientation begins at unit pixels, thereby reducing overall picture quality. That is, a bent electric field is formed at edges of pixel electrodes, the bent electric fields being formed in each unit pixel that is slightly separated from the next. At the areas where alignment begins in each unit pixel, the direction of this bent electric field and the direction of the bent alignment of the liquid crystal molecules are in opposing directions, resulting in the broken alignment of the liquid crystal molecules in these locations.
The present invention has been made in an effort to solve the above problems.
It is an object of the present invention to provide a liquid crystal display having a wide viewing angle and fast response speed, and in which liquid crystal molecules of the liquid crystal display have a uniformly bent alignment.
To achieve the above object, the present invention provides a liquid crystal display comprising a first substrate including wiring that intersects to define unit pixels, and a first electrode provided in each unit pixel; a second substrate opposing the first substrate and including a second electrode formed over an entire area of the second substrate, the first and second electrodes forming an electric field when a voltage is applied to the first and second electrodes; a liquid crystal formed by injecting liquid crystal material between the first and second substrates, the liquid crystal material being comprised of liquid crystal molecules that are horizontally oriented in one direction and increasingly bent as approaching an imaginary center plane, which is parallel and equidistant to the first and second substrates, when the electric field is formed between the first and second substrates, thereby being symmetrical about the center plane; and a buffer electrode provided under the first electrode and extending past an edge of the same at an area where orientation of the liquid crystal molecules begins in the unit pixel.
According to a feature of the present invention, the wiring includes gate lines for transmitting gate signals and data lines for transmitting image signals, where the data lines cross the gate lines.
According to another feature of the present invention, the first substrate further includes thin film transistors formed at regions where the gate lines and the data lines cross, the thin film transistors having gate electrodes connected to the gate lines, source electrodes connected to the data lines, drain electrodes provided opposite the source electrodes with reference to the gate electrodes, and a semiconductor layer.
According to yet another feature of the present invention, the buffer electrode is formed on a same layer as the wiring.
According to still yet another feature of the present invention, the buffer electrode is electrically connected to the first electrode.
According to still yet another feature of the present invention, the buffer electrode is formed in line with the wiring.
In another aspect, the present invention provides a liquid crystal display comprising a first substrate including wiring that intersects to define unit pixels, and a first electrode provided in each unit pixel; a second substrate opposing the first substrate and including a second electrode formed over an entire area of the second substrate, the first and second electrodes forming an electric field when a voltage is applied to the first and second electrodes; and a liquid crystal layer formed by injecting liquid crystal material between the first and second substrates, the liquid crystal material being comprised of liquid crystal molecules that are horizontally oriented in one direction and increasingly bent as approaching an imaginary center plane, wherein the center plane is parallel and equidistant to the first and second substrates, when the electric field is formed between the first and second substrates, thereby being symmetrical about the center plane, wherein an aperture is formed in either the first electrode or the second electrode in an area where orientation of the liquid crystal molecules begins in the unit pixels.
According to a feature of the present invention, there is further provided a buffer electrode under the first electrode and extending past an edge of the first electrode at an area where orientation of the liquid crystal molecules begins in the unit pixel.
According to another feature of the present invention, the edge of the first electrode under which the buffer electrode is provided is the edge closest to a center of the second electrode.
According to yet another feature of the present invention, the aperture and the buffer electrode are formed in line with the wiring.
According to still yet another feature of the present invention, the wiring includes gate lines for transmitting gate signals and data lines for transmitting image signals, where the data lines cross the gate lines.
According to still yet another feature of the present invention, the first substrate further includes thin film transistors formed at regions where the gate lines and the data lines cross, the thin film transistors having gate electrodes connected to the gate lines, source electrodes connected to the data lines, drain electrodes provided opposite the source electrodes with reference to the gate electrodes, and a semiconductor layer.
According to still yet another feature of the present invention, the buffer electrode is formed on a same layer as the wiring.
According to still yet another feature of the present invention, the buffer electrode is electrically connected to the first electrode.
According to still yet another feature of the present invention, if the aperture is formed in the second electrode, an edge of the aperture closest to the center of the unit pixel is provided over the first electrode.
In yet another aspect, the present invention provides a liquid crystal display comprising a first substrate including wiring that intersects to define unit pixels, and a first electrode provided in each unit pixel; a second substrate opposing the first substrate and including a second electrode formed over an entire area of the second substrate, the first and second electrodes forming an electric field when a voltage is applied to the first and second electrodes, and also including a black matrix formed in the unit pixel and having an aperture; and a liquid crystal layer realized through liquid crystal material injected between the first and second substrates, the liquid crystal material being comprised of liquid crystal molecules that are horizontally oriented in one direction and increasingly bent as approaching an imaginary center plane, which is parallel and equidistant to the first and second substrates, when the electric field is formed between the first and second substrates, thereby being symmetrical about the center plane, wherein a pretilt angle of the liquid crystal molecules is different in a first region corresponding to the unit pixel and a second region corresponding to the wiring or the black matrix.
According to a feature of the present invention, the pretilt angle of the first region is smaller than the pretilt angle of the second region.
A method for manufacturing a liquid crystal display comprises the steps of producing a first substrate including wiring that intersects to define unit pixels, and a first electrode provided in each unit pixel; producing a second substrate including a second electrode formed over an entire area of the second substrate, the first and second electrodes forming an electric field when a voltage is applied to the first and second electrodes, and also including a black matrix formed in the unit pixel and having an aperture; performing a first orientation process in the same direction on the first and second substrates such that liquid crystal molecules of liquid crystal material to be provided between the substrates have a particular pretilt angle; aligning and connecting the first and second substrates such that a predetermined gap is formed therebetween; and performing a second orientation process such that the liquid crystal molecules have a different pretilt angle in a first region corresponding to the wiring or black matrix and in a second region corresponding to the unit pixel.
According to a feature of the present invention, the second orientation process is performed by irradiating light while using the wiring or black matrix as a mask.
According to another feature of the present invention, the pretilt angle of the second region is smaller than the pretilt angle of the first region.
In still yet another aspect, the present invention provides a liquid crystal display comprising a first substrate including wiring that intersects to define unit pixels, and a first electrode provided in each unit pixel; a second substrate opposing the first substrate and including a second electrode formed over an entire area of the second substrate, the first and second electrodes forming an electric field when a voltage is applied to the same; and a liquid crystal layer realized through liquid crystal material injected between the first and second substrates, the liquid crystal material being comprised of liquid crystal molecules that are horizontally oriented in one direction and increasingly bent as approaching an imaginary center plane, which is parallel and equidistant to the first and second substrates, when the electric field is formed between the first and second substrates, thereby being symmetrical about the center plane, wherein a pretilt angle of the liquid crystal molecules is in the range of 10-25xc2x0.
According to a feature of the present invention, the liquid crystal display further comprises a protrusion pattern in each unit pixel covering an edge of the first electrode where orientation of the liquid crystal molecules starts.
According to another feature of the present invention, the protrusion pattern has an anisotropy of between 3 and 7.
According to yet another feature of the present invention, the wiring includes gate lines for transmitting gate signals and data lines for transmitting image signals, where the data lines cross the gate lines.
According to still yet another feature of the present invention, an orientation direction of the liquid crystal molecules is parallel to the data lines or the gate lines.
According to still yet another feature of the present invention, the liquid crystal display further comprises a layer for blocking light, the layer being formed under the first electrode where orientation of the liquid crystal molecules starts in the unit pixels.
According to still yet another feature of the present invention, the layer for blocking light is formed on a same layer as the gate lines.
According to still yet another feature of the present invention, the layer for blocking light overlaps the first electrode to form a storage capacitance.